1. Field of the Invention
The present invention relates to digital medical and/or dental imaging systems which utilize reusable photo-stimulable phosphor (PSP) imaging plates, and more particularly, to a restoration assembly which erases or clears the residual information from a previous x-ray exposure prior to reuse of the imaging plate.
2. Description of the Prior Art
Photo-stimulable phosphor (PSP) imaging plates record an image as a result of x-ray exposure. The exposed imaging plate is then scanned or read by a scanner which digitally stores the image in a computer processing unit. Since the imaging plates are reusable, the residual information must be erased from the imaging plate before it is reused. There are automatic imaging systems available wherein the imaging plates are not manually handled and these systems perform this erasure function internally.
However, there are many systems that require manual handling of the imaging plates such as those associated in the dental arts with dental scanners or image readers. In these systems, the user must expose the imaging plates to a light source of a known power for a sufficient length of time so that the total energy per unit area has adequately erased or deleted the previous residual image data. Typically an erasure of 95.5 percent is sought. Such erasing in a manual system requires a 60,000 LUX-second of fluorescent light for intraoral imaging plates and double that amount for extraoral imaging plates. If incandescent light is utilized, the erasure requires 120,000 LUX-second of incandescent for intraoral imaging plates and twice that amount for extraoral imaging plates. Other arguments by physicists have indicated that energy of as much as 750,000 Lux-sec is required for adequate or acceptable erasing of such image plates.
The existing technology associated with the manual handling of the image plates recommends the placing of the imaging plates face down on the horizontal surface of a view box or clipped to the vertical surface of a wall mounted view box. The lowest measured light intensity at any given point on the view box would determine the amount of time required for restoration by dividing the exposure requirement by this intensity.
This existing procedure introduces several factors which adversely affect imaging plates. The surface of the view box may be dusty or have particulate matter adhering thereto which in turn adheres to the image surface of the imaging plate and thereby possibly degrading subsequent images. Still further in positioning the imaging plate on the view box and removing it from the view box, the imaging surface of the imaging plate may be scratched leading to premature degradation and may affect any subsequent exposure images. Still further there may be surface imperfections on the view box which will cause shadows on the imaging plate thereby not allowing complete erasure of the plates at these locations. Additionally, manipulating the plates on such surfaces invariably cause the users to touch the imaging surface of the imaging plate leading to the deposit of body oils and acids on the sensitive surface which further prematurely degrades the plates useful life and affect any subsequent images. Finally, since light sources decrease unpredictably in their light emitting intensity with time, the light box emitting light intensity must be monitored regularly to assure adequate erasure or else excessive erasure time must be given.